1. Field of the Invention
The present invention relates to the apparatus and method for image configuring capable of configuring a single object image of high resolution from a plurality of reduced object images of low resolution obtained by a compound-eye camera using a plurality of micro lenses.
2. Description of the Related Art
As an image input apparatus that effectively obtains various image information of high quality, image input apparatuses having structure of obtaining an object image by single optical system that is opposing to the object as a photogenic subject, such as digital cameras and video cameras, have been widely used. However, in these days, for the purpose of downsizing and tinning the image input apparatus, compound-eye cameras mimicking the compound-eye structure of such as insects have been developed.
A compound-eye camera includes a micro-lens array in which a plurality of micro lenses are arranged, as well as a photo detector formed in a planar condition, and obtains a plurality of reduced object images of low resolution focused on the photo detector by using the micro lens array. Here, when the number arrays of one-dimensional direction (one column) of the micro lens array is assumed as N, compound-eye camera can observe an observation area nearly same as the one for single-eye camera at 1/N times of the focal length (1/N thickness) of single-eye camera by using the photo detector of the same level. This significantly realizes the thinning and downsizing of the compound-eye camera compared to the single-eye camera capable of observing the same observation area, and allows a compound-eye camera to obtain a bright image of the same level as the one obtained by a single-eye camera.
FIG. 8 shows an optical system of a single-eye camera ((a) single-eye optical system) and an optical system of a compound-eye camera ((b) compound-eye optical system) in a general manner.
As can be understood by comparing FIGS. 8(a) and (b), since each of the focal lengths (in FIG. 8, indicated at f/N) of the micro lenses 80 are minimal, a compound-eye camera can be structured as a significantly downsized and thin apparatus, compared to a single-eye camera capable of obtaining an image of the same-level in brightness.
However, while the compound-eye camera can be thin, small and capable of obtaining a bright image, it has a defect that each of the reduced object images is of low resolution. Therefore, it is required to configure a single object image of high resolution by conducting image processing to these plurality of reduced object images.
As a method for obtaining a single high-resolution image from a plurality of reduced object images, for example, a method for image reconfiguring by means of such as sampling method and pseudo inverse method has been disclosed in J. Tanida, T. Kumagai, K. Yamada, S. Miyatake, K. Ishida, T. Morimoto, N. Kondo, D. Miyazaki, and Y. Ichioka, “Thin Observation module by bound optics (TOMBO): concept and experimental verification,” Appl. Opt. 40, 1806-1813 (2001) (hereinafter referred to as “non-patent literature 1”). The sampling method is for reconfiguring a single object image by superposing reduced object images basing their centroid positions. The pseudo inverse method is firstly for indicating the object as a photogenic subject and the reduced object images by vectors, and describing a point spread function of optical system by matrix. It then for reconfiguring a single object image by calculating the inverse matrix of the point spread function mathematically.
Additionally, in Japanese Patent Publication No. 2003-141529 (hereinafter referred to as “patent literature 1”), a method for image reconfiguring that firstly calculates a shift amount of a plurality of reduced object images through correlation calculation between these reduced object images, and consequently obtains a high-resolution image by rearranging each pixel of a plurality of reduced images on a same area based on the above shift amount has been disclosed.
On the other hand, as a digital super-resolution technology based on an image obtained by a single-eye camera, an iterative back projection method as an iterative algorithm that generates a single high-resolution image from a plurality of low-resolution images having overlaps though having different observation positions has been disclosed in M. Irani and S. Peleg, “Improving resolution by image registration, CVGIP: Graphical Models and Image Processing”, 53, pp. 231-239 (1991) (hereinafter referred to as “non-patent literature 2”).